The study found that 85% of under-16s were unaware that they need a work permit from their local authority before they can accept paid employment.

NSPCC safeguarding in business adviser Charlie Monkcom said: “Part-time employment is almost a rite of passage for young people. It gives them independence, a good work ethic and access to their own income. But too many children are working without the proper safeguards in place.

“Legislation must be tightened up to protect children from significant harm and abuse.”

Employers can be prosecuted for hiring children without valid work permits.